1. Question: [Thursday, 23rd MarCheshvan 5783]
I would like to know if my and my 2nd wife’s son who is our firstborn is eligible to receive a double portion as the Torah dictates if he was born after I had a daughter from a previous marriage?
He is not considered a firstborn regarding inheritance and is hence not eligible to receive a double portion.
Explanation: A son who was born after his father already had a daughter is not considered a firstborn regarding inheritance and is hence not eligible to receive a double portion. This applies whether the daughter was born to the son’s mother [i.e. maternal and paternal older sister] or was born to a different mother [i.e. only a paternal sister]. This applies even if the son is his mother’s first born.
Sources: Michaber C.M. 277:8; Admur O.C. 470:2; Tur 277:9; Rambam Nechalos 2:9; Mishneh Bechoros 46a; Bava Basra 111b